Manufacture of salts of 2:1-hydroxynaphthoic acid



Patented Dec. 12, 1950 UNITED STATES PATENT OFFICE- MANUFACTURE OF SALTS F 2:1-

HYDROXYNAPHTHOIC ACID Eric B. Higgins, Tewin Wood, England, assignor 1110., county of New York,

to Tewin Industries N. Y.

No Drawing. Application March 31, 1949, Serial No. 84,759. In Great Britain April 5, 1.948

4 Claims.

Practically quantitative yields, that to say, 50 per cent upon the naphtholate employed are readily obtained if the naphtholate is subjected to the action of the carbon dioxide whilst in suspension in an agent, for example, toluene, at the boiling point of the liquid. (Oddo 8; Manueli, Gazzeta Chimica Italiana 31, II, 244, 1901.) It would seem clear, therefore, that if this latter method is adopted, as the liberated free betanaphthol is freely sol ble in toluene whereas the sodium hydroxynaphthoate is virtually insoluble, filtration of the mass and subsecuent extraction with fresh solvent should provide a means of producing the disodium 2:1 hydroxyn-aphthoate substantially free from material containing free hydroxyl-group-s.

In fact, however, it is found that great mechanical difficulties are encountered in such a process on account of the physical condition of the precipitated material, and moreover, the process does not, in fact, yield a product which can be relied upon not to contain free hydroxyl groups. This is doubtless due to the fact that both the starting material-sodium naphtholate, and the end product-sodi m 2:1 hvdroxynaphthoate are insoluble in the toluene, which militates against com l te reaction, and that the reaction is not strictly confined to the route as given above, but can proceed according to either or both of the equations:

In fact, it has been found that at temperatures of 90-l00 C., the reaction can proceed wholly according to the above Equation I, that is to say, the method of Schmidt, (Journal fur Praktische Chemie (2) 31, 397, 1885) and, moreover, without the necessity of employing superatmospheric pressures.

It has now been found that yields of dlsodium 2:1 hydroxynaphthoate, quantitativ in respect 2 to the naphtholate used, can readily be obtained if the reaction between the dry sodium betanaphthalene is a very suitable vehicle for this accordance with the present invention, in the presence of an additional equivalent quantity of free metallic sodium, thus:

The reaction is best carried out in a chemically indifferent liquid and, with the greatest advantage, if the liquid is a solvent for the naphtholate as well as for free beta-naphthol, and it has further been found by experiment that tetrahydronaphthalene is a very suitable vehicle for this purpose.

In order that the invention may be more clearly understood and readil carried into practice, various methods, will now be given by way of example.

Example I In a vessel arranged to be -heated and supplied with a reflux condenser and provided with a means of introducing carbon dioxide gas and, preferably, a stirrer or other means of agitation, 2800 litres of tetrahydronaphthalene are added to 144 kilogms of beta-naphthol, and 46 kilogms of sodium introduced. The air is referably, though not necessarily, displaced from the apparatus by nitrogen or hydrogen or is evacuated, and, with stirring, the temperature is raised to the melting point of sodium at which point reaction becomes rapid, hydrogen being evolved. Stirring and heating must be carefully regulated during the early stages so as to prevent the reaction from becoming too violent. The. state of reaction can be judged by the evolution of hydrogen which accompanies it. As the evolution of gas slackens, the temperature is raised till the tetrahydronaphthalene is boiling, and the boiling continued until the evolution of gas is complete or negligible. The reaction according to th equation:

is now substantially complete and the naphtholate forms a clear pale yellow solution. In these circumstances, the beta-naphthol is not hydrogenised to any significant extent. Carbon dioxide is then passed into the boiling solution, superatmospheric pressure being unnecessary. The hydroxynaphthoate begins at once to precipitate as it is practically insoluble in tetrahydronaphthalene and hydrogen is again evolved, according to the equation:

The duration of this stage of the reaction is mainly dependent upon the efllciency of the means used to ensure contact between the gas and of melted under tetrahydronaphthalene is then added, the reflux condenser set in operation and the reacting .fiuid- Simple bubbling of the gas through the liquid will produce the desired end, though slowly, but best results are realised if a cone or propeller type of stirrer is employed which forces the supernatant gas repeatedly through the violently agitated liquid. The end of the reaction can be ascertained b the cessation of evolution of hydrogen. The yield is substantially quantitative in respect to the betanaphthol employed.

The product may be isolated by distillation of the solvent, preferably under sub-atmospheric pressure or by filtration or by centrifugal action, but air must at all times be rigidly excluded since the di-salt of 2:1 hydroxynaphthoic acid in the dry'state is-destructively oxidised with great ease.

Alternatively, the 'di-salt be caused to enter into further desired reactions in suspension in the 'tetrahydronaphthalene without actual separation.

'redu'ce'o. "and, in such a case, it is preferable to use a higher'pro'port on of solvent than that indicated at the beginning of this example.

Example-II In'a n apparatus as indicated'in Example I, but

:with the addition of means for direct distillation, 144 kilogms of beta-naphthol, 40 kilogms of solid caustic soda in coarse powder and 3000 litres of tetrahydronaphthalene, are introduced. Air-is removed or displaced from the apparatus and with constant stirring, the temperature is raised until distillation begins and the tetrahydronaphthalene-water azeotrope begins to distil according to the equation:

Distillation is continued until the distillate runs clear and the thermometer shows the boiling point of pure tetrahydronapht'halene. 23 kilogms metallic 'sodiumconveniently previously treatment with carbon dioxide begun and carried through as described in Example I.

Example III filtered extract is transferred with protection from air to the apparatus as indicated in Example II, and the reactionth'en conducted as therein described.

EramplaIV In an apparatus as indicated inExa'mples I "and II, '72 kilogms of beta-napht'hol is dissolved in 3000 litres of diphenylet'her (CeHshO and converte'd to the 'naphtholate either by the ac- 'tion of 16.5 kilogms of sodium according to the method described inExampleI or by reaction with '20 .kilogms of caustic soda as explained in Example II. The solution is brought to a temperature of 98100 C. and carbon dioxide gas introduced until no further absorption takes place. The reaction is slow and may occupy from 10 to 12 hours. At this stage the reaction, according to the equation:

"ZCmI-IGOHCOONa}-l laz=2C1ol-isONaCOONa+Hz In all cases, the reaction is satisfactory and practical if conducted under atmospheric pressures butmay be accelerated by increasing the solu bility Of'COz in the solvent by the use ofsuperatmospheric pressure should the corresponding added mechanical complication of the apparatus be judged less significant. Sodium amalgam may be used instead of sodium metalbut does not afford any chemical'advantage. I claim:

1. A process for the production of diso'dium'fZzl hydroxynaphthoic acid substantially free fr-m material containing free hydroxyl groups which comprises heating sodium beta naphtholate in a chemically inert liquid to a temperature of between .98" 'C. and .210 C. in the presence of carbon dioxide and at least an equivalentquan- .t'ity of metallic sodium.

2. .A ,process according to claim 1, in which the chemically inert liquid is a solvent for .betanaphthol and thesodio derivative of the same.

3. A process "for the production of diso'dium 2:1 hydroxynaphthoic acid substantially free from material containing free hydroxyl groups which comprises heating sodium beta naphthalate dissolved in diphenyl etherto a temperature of between 98 C. and 210 C. in thepresence of carbon dioxide and at least an equivalent quantity of metallic sodium.

a. Aprocess for the production of disodium 2:1 hydroxynaphthoic acid substantially free from material containing free hyroxylgroups which comprises heating sodium betanaphtholate dis- -solved in tetrahydronaphthalene to a temperature of between 98 C. and 210 C. in thepresence or carbon dioxide and at least .an equivalent quantity of metallic sodium.

ERIC B; I'HGGINS.

REFERENCES .CITED The following references are-of reoordin the file of this patent:

UNITED STATES PATENTS Reifi Aug. 26,

Certificate of Correction Patent No. 2,534,022 December 12, 1950 ERIC B. HIGGINS It is hereby certified that error appears in the Printed specification of the above numbered patent requiring correctlon as f0 lows:

Column 2, line 3, for ma hthalene is a very suitable vehicle for this read naphtholate and carbon diam-tale is carried out in;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 13th day of March, A. D. 1951.

THOMAS F. MURPHY,

Assistant Gommim'oner of Patents. 

1. A PROCESS FOR THE PRODUCTION OF DISODIUM 2:1 HYDROXYNAPHTHOIC ACID SUBSTANTIALLY FREE FROM MATERIAL CONTAINING FREE HYDROXYL GROUPS WHICH COMPRISES HEATING SODIUM BETA NAPHTHOLATE IN A CHEMICALL INERT LIQUID TO A TEMPERATURE OF BETWEEN 90*C. AND 210 DEGREES IN THE PRESENCE OF CARBON DIOXIDE AND AT LEAST AN EQUIVALENT QUANTITY OF METALLIC SODIUM. 